McFARLAND, Wis.--Don Peterson, a builder in this Wisconsin town, recently took a large polystyrene foam cup--the sort you crumple up and throw away the moment you're through with it--and covered it with a thin layer of specially formulated stucco.

When the masonry covering was dry, he stood on the cup. So did several other grown men. It easily supported their weight.

Peterson went to all this trouble to prove a point: When you combine flimsy Styrofoam with brittle masonry, the resulting "sandwich" is so strong it becomes a viable building material. You could even build houses with it.

Given the right thickness of Styrofoam and the acrylic- and fiberglass-reinforced stucco that he calls Insulcrete, you could produce houses that are so durable and energy efficient they would pay for themselves several times over in saved heating and cooling costs.

Built Prototype

To test his theory, Peterson built a small prototype two years ago using 12-inch wide Styrofoam blocks with one-third of an inch of stucco skin applied on each side. Then he parked a Mack truck on the roof, and not even a hairline fracture appeared in the ceiling. Next he filled the building with conventional furniture, including a sofa and a TV, and set the contents on fire.

The heat was so intense--1,500 degrees Farenheit, according to the firemen who conducted the test-- that when it was all over, most of the debris could be swept away with a yard broom. Even so, the house was unchanged apart from blackened walls and some slight melting of the foam in two places where the sofa had stood. Repair work was largely confined to a new coat of paint.

Now that prototype serves as an office for Cubic Structures, the company Peterson founded to market the new super-insulated home. Currently the company is overseeing the erection of its 24th foam home, which it offers in 12- and 10-inch wall thicknesses. An "economy model" with 8-inch walls and a modified frame is also under construction.

Peterson, a one-time auto salesman who wanted to deal in products that lasted a lifetime rather than the allotted span of a used car, started a business 14 years ago that put a new and durable face on old buildings.

Sheathing Building

Taking an idea that originated in Europe and adding a few refinements of his own, he reconditioned old buildings by sheathing them with polystyrene foam boards which were then covered with Insulcrete. The protective finish could be made to imitate brick or other masonry finishes.

At the time, the owners of the buildings were looking only for an improved appearance but soon discovered that they had received far more for their money. Their buildings started to perform much better as well. They cost far less to heat and cool for two reasons: the insulating nature of the foam and the fact that the masonry finish dramatically reduced air leakage.

Peterson, noting that the foam-masonry combination was unusually strong, soon realized that the foam didn't merely belong in or on the wall; it could, in fact, be the wall, given a protective covering. Some months later the prototype was built.

A Cubic Structures home is essentially a post-and-beam structure, but in this instance the load-bearing frame is made of Insulcrete poured into hollow cores at each end of the eight-foot-long foam blocks. The concrete frame serves two purposes: it gives added strength to the structure and it ties the house to its foundation. Because foam is so light, a strong gale might tip it over, were it not so effectively fastened to the ground.

Foam Blocks for Walls

A Cubic Structures home is built this way: After the foundation is poured, the foam blocks are stacked in place to form the walls. Then the Insulcrete posts are poured in place.

A similar Insulcrete bond encircles the house at the top of the wall. The roof, made of foam blocks supported by conventional 2-by-12 rafters, goes on next.

Nowhere is there any thermal bridging (wood or concrete linking the interior warm air with the outside cold). Finally, the Insulcrete skin is troweled on. The exterior can have a pebble-aggregate, brick, or any one of several masonry finishes.

The result is an exceptionally tight house with 12-inch R-46 walls and a 14-inch R-54 roof that also shuts out outside noise to a remarkable degree. A Madison couple had long been conscious of noise from an open-air skating rink near their home.

Then two years ago they had a Cubic Structures house erected right opposite the rink. To their delight, keeping out the noise is now as simple as shutting the door, which is the natural thing to do in winter anyway.

This same couple finds that they can heat their 1,500-square-foot home for little more than $100 a season using electric baseboard heat (not the most efficient form of electric heat) with electricity costing 5 cents a kilowatt-hour.

A Cubic Structures home is competitive with double-wall superinsulated stud-built homes "which are less fireproof," Peterson said. So, to offer homes competitive with conventional construction, his company has developed a modified version of the Cubic Structures house--though with R-31 walls and a natural air exchange rate of only 0.10 per hour it still qualifies as a super-insulated structure. The modified home uses commercially available Dow Styrofoam (blue board) and wood studs in place of the poured Insulcrete posts.

A homeowner's portfolio including floor plans and test data is available for $10 from Cubic Structures, 4307 Triangle Street, McFarland, Wis. 53558.